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δ‐Methyl Branching in the Side Chain Makes the Difference: Access to Room‐Temperature Discotics
Author(s) -
Kirres Jochen,
Knecht Friederike,
Seubert Philipp,
Baro Angelika,
Laschat Sabine
Publication year - 2016
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201501166
Subject(s) - triphenylene , mesophase , mesogen , alkoxy group , discotic liquid crystal , branching (polymer chemistry) , side chain , liquid crystal , differential scanning calorimetry , crystallography , melting point , materials science , ether , crown ether , chemistry , organic chemistry , alkyl , polymer , liquid crystalline , thermodynamics , physics , ion , optoelectronics
Although discotic liquid crystals are attractive functional materials, their use in electronic devices is often restricted by high melting and clearing points. Among the promising candidates for applications are [15]crown‐5 ether‐based liquid crystals with peripheral n ‐alkoxy side chains, which, however, still have melting points above room temperature. To overcome this problem, a series of o ‐terphenyl and triphenylene [15]crown‐5 ether derivatives was prepared in which δ‐methyl‐branched alkoxy side chains of varying lengths substitute the peripheral linear alkoxy chains. The mesomorphic properties of the novel crown ethers were studied by differential scanning calorimetry, polarizing optical microscopy, and X‐ray diffraction. δ‐Methyl branching indeed lowers melting points resulting in room‐temperature hexagonal columnar mesophases. The mesophase widths, which ranged from 87 to 30 K for o ‐terphenyls, significantly increased to 106–147 K for the triphenylenes depending on the chain lengths, revealing the beneficial effect of a flat mesogen, due to improved π–π interactions.